Vented rotary lawn mower

ABSTRACT

A vented rotary lawn mower having wheels for ground supporting the mower and having a handle for guiding the mower. The mower has a deck or housing which encloses a cutter blade, and the deck or housing has a plurality of air vents which permit air to enter the top of the deck or housing and to pass downwardly to the location of the cutter blade, and thereby introduce air into the housing and assist in the flow of air through the housing and out the exhaust. The mower is shown to be power propelled, and it has a drive which is under the control of the operator for driving the ground wheels. Also, the mower handle is pivoted on the mower housing in a manner and at a point to effect easy and efficient guiding of the mower through the handle.

United States Patent i191 Erickson et a l.

[4 1 Mar. 5, 1974 v VENTED ROTARY LAWN MOWER [75] Inventors: Donald G. Erickson, Racine; Vernon R. Kaufman, C'edarburg, both of Wis.

[73] Assignee: Jacobson Manufacturing Company,

Racine, Wis.

22j Filed: Jan.l7,1973

21 Appl.No.:324,298

52 US. on. 56/3202 [51] Int. Cl A0ld 55/18 [58] Field of Search 56/320.'1, 320.2, 255, 13.3, 56/ 13.4

[56] References Cited UNITED STATES PATENTS 7 3,178,872 4/1965 Swindler 56/13.4

3,049,854 8/1962 Denney 56/134 X 3,220,170 11/1965 Smith et al 56/255 Primary Examiner-Russell R. Kinsey Assistant ExaminerJ. N. Eskovitz Attorney, Agent, or Firm-Arthur Jv Hansmann [5 7] ABSTRACT A vented rotary lawn mower having wheels for ground supporting the mower and having a handle for guiding the mower. The mower has a deck or housing which encloses a cutter blade, and the deck or housing has a plurality of air vents which permit air to enter the top of the deck or housing and to pass downwardly to the location of the cutter blade, and thereby introduce air into the housing and assist in the flow of air through the housing and out the exhaust. The mower is shown to be power propelled, and it has a drive which is under the control of the operator for driving the ground wheels. Also, the mower handle is pivoted on the mower housing in a manner and at a point to ef-,

fect easy and efiicient guiding of the mower through the handle.

11 Claims, 8 Drawing Figures PATENTED 4- sum 1M 1 VENTEI) ROTARY LAWN MOWER This invention relates to a vented rotary lawn mower, and, more particularly, it relates to a rotary lawn mower which has provision for the optimum and efficient flow of air through the mower while the mower is being operated for cutting grass.

BACKGROUND OF THE INVENTION Rotary mowers are in common use today, and they find a useful purpose in mowing grass in many different mowing conditions, such as tall grass, thick grass, irregular terrain, and the like. Further, rotary mowers are particularly useful in the collection of the grass which has been cut, and, for this purpose, the bag collector is popular and in common use today.

For efficient and desirable mowing, the rotary mower depends upon a flow of air which exists within the mower housing and which continues through the mower outlet and beyond the mower itself where the clippings are conveyed for deposit or collection In this regard, the rotation of the cutter blade itself generates introduced into the housing from the-location below the apron or depending portion of the housing or deck itself. Under many conditions of mowing, an adequate supply of incoming air is not permitted to flow under the housing apron and into the housing itself. That is, when the grass is dense and/or wet, then air cannot enter the housing in sufficient quantity to perform its function of creating the air stream which conveys the cut clippings around the housing and therefrom. The prior art is also aware of mowers which introduce air into the housing at the top of the housing. For example, see U, S. Pat. Nos. 2,953,888 and 2,877,616 in the harvester type cutters, and U. S. Pat. Nos. 3,189,910 and 3,423,912 for rotary lawn mowers. However, those disclosures are not of vented mowers for the purpose of preventing choking of the mower in the flow of inlet air.

Accordingly, it is the purpose of the present invention to provide a rotary mower housing wherein. an adequate supply of air can enter the housing for proper mowing and conveying actions, under all conditions of mowing.

Another object of this invention is to provide a vented rotary mowerhousing wherein efficient grass cutting and conveying can be carried out but without impeding the normal action of the cutting and without diminishing the strength of the mower nor imparing the safety features commonly provided in present day mowers. Specifically, the mower of this invention is arranged'with vents which permit the inlet of air, regardless of the mowing conditions, and the mower is not weakened in its structural strength, and there is no less ening of the safety aspects of the modern day rotary mower. Further, the mower of this invention, while it is providing vents for the inlet of air, does not result in- 2 the clogging of the vents by the blowing and conveyance of the cut grass.

Still further, the present invention provides a vented rotary mower housing wherein the mower cannot starveitself for necessary air inside the housing, and thus the housing does not tend to be under vacuum conditions at the interior, and therefore the mower is at least somewhat in air suspension where the vents of the mower of this invention permit adequate air pressure and air supply inside the mower housing. Such interior air supply and pressure'as provided by the vented housing of this invention also serve to prevent packing or clogging of the cut grass on the interior of the mower housing. Further, the air vents of the mower of this invention are arranged and located to effect optimum inlet of air, at the front portion of the mower, and to maintain adequate mower housing strength.

Other objects and advantages will become apparent upon reading the following description in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a mower showing a preferred embodiment of this invention.

FIG. 2 is a bottom plan view of FIG. 1, with parts removed.

FIG. 3 is a side elevational view of FIG. 1, with parts removed, and with the engine added thereto.

FIGS. 4, 5 and 6 are enlarged sectional views taken respectively along the lines 4-4, 5-5, and 6-6 of the mower deck of FIG. I.

FIG. 7 is an enlarged sectional view taken along the lines 77 of FIG. 1.

FIG. 8 is a top plan view of'FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The drawings show a rotary lawn mower having a housing It) and the usual ground supporting wheels 11. FIGS. I and 2 show the top and bottom views, respectively, of the housing 10 which is shown to be generally circularly shaped for enclosing the lawn cutter bar 12 which is rotatably mounted in the housing It) in the usual manner. The housing It) has its usual depending skirt portion 13 at the circumference of the circularly shaped housing, and the skirt 13 terminates in its usual lower edge 14 which is disposed immediately above the ground on a horizontal plane, such as also seen in FIG. 3. That is, the wheels 11 are customarily arranged for mobilely-supporting the housing 10 and for positioning the housing depending edge 14 immediately above the ground and in physical contact with the grass being mowed. Thus, the grass blades actually extend up to and above the level of the housing edge 14, in the normal use of the rotary mower.

The drawings further show that the housing 10 has an annulus 16 through which the grass cutting ends 17 of the cutter bar 12 arerotated, for cutting the grass in the usual manner. Also, the housing 10 has its usual tangentially extending outlet 20 which extends off the circular annulus 16 for directing the cut grass rearwardly and to the side of the forward advancing mower. ,Of course the cut grass may be directed into a grass catcher bag which is not shown but which is in common use today and which would be mounted on the mower outlet 18. Thus, as seen in FIG. 2, the .cutter bar 12 would rotate to have its cutting ends 17 moving'in the path and direction of the arrow designated A in FIG. 2, and this is also as seen and indicated in FIG. 6 where the cutter 12 is somewhat re-positioned relative to its shown position in FIG. 3.

Thus, the mower, being supported by the wheels 11 on the ground, is moved forwardly, as seen in FIG. I, so that the mower has a front end 19, and the cut grass moves out the mower discharge chute 21 which is directed to the right side and rearwardly. FIG. 1 also shows a fragment of the mower handle 22 which is of a well-known construction and which'is attached to the mower housing in a manner described later. The operator therefore directs and guides the mower in the forward direction and the cutter bar 12 rotates in the clockwise direction, as seen in FIG. 1, and the cut grass is blown around the mower housing and along the annulus 16 and through the outlet 21, by virtue of the air and physical force imparted by the rotation of the cut ter bar 12, all in the usual manner. The usual prime mover 23, and it may be a gasoline engine or an electric motor, is suitably mounted on the mower housing 10 and extends thereabove and has a drive shaft 24 extending downwardly to engage the cutter bar 12 for rota'ting the bar 12. The bar 12 is shown to have a hub 26 affixed thereto for receiving and keying with the drive shaft 24, all in the usual manner.

' The important feature with respect to the mower deck or housing 10 is the provision of air vents which permit the inlet of air into the housing 10 for the purpose of providing the necessary air flow in the movement of the cut grass in the annulus 16 and through the, mower outlet 21. To this end, the mower housing 10 is provided with a plurality of air vents or openings 27 which are disposed in themower housing top 28 and which are shown to be disposed ina circular pattern extending for slightly more than one half the complete circular configuration of the mower top 28 at a location radially inwardly from the cutting annulus 16. With this arrangement, air is permitted to enter the mower housing 10 at the top of the housing 10 and to create a flow of air radially outwardly and into the annulus l6 and therealong at the location where the cut grass is being impelled and directed for exhausting it from the mower housing 10. Thus the vents 27 are located on a semicircular pattern and are disposed adjacent the mower outlet 21 and toward the front end of the housing It),

where the cutter bar 12 is doing the majority of the grass cutting and where it is imparting the air flow for the conveyance of the grass out of the housing 10.

The drawings further show that the housing 10 is provided with a circular section 29 which is depressed in the mower top 28 and which defines the radially inner wall 31 locating the annulus 16. Also, circular ribs 32 substantially in the direction of the arrow B, but, the

-' grass cannot readily reach the vents 27, to clog the vents 27, because of the relative positions of the vents 27 and the webs34. That is, the webs 34 prevent the cut grass from being blown and thrown into the vents 27. Further, the webs 34 serve to create a Venturi action so that the air will flow downwardly through the vents 27 and into the housing 10 and into the'annulus 16, as desired. Thus, the mower housing has the portions 36 which are solid portions and which, along with the webs 34, provide the necessary structural strength for the mower top 28, and the portions 36 are extending to the upstream side of the webs 34 while the vents 27 are immediately adjacent the webs 34 on the downstream side thereof.

The vents 27 are therefore available for the inlet of air at least under circumstances where the mower is opcrating in thick or heavy grass which tends to block the FIG. 5. With this arrangement, the cut grass is moving passage of air into the housing 10 at the location of the mower apron lower edge 14. Especially under those conditions of mowing, ample air cannot flow into the annulus to for conveying the clippings through the mower outlet 2i, and the mower actually suffocates.

With the vents 27, air can flow downwardly into the mower housing 10 and outwardly into the annulus l6, and the air can then adequately move in the annulus 16 to convey the clippings, as preferred and desired.

Of course the provision of the vents in the housing It), as shown and described, can be utilized with rotary mowers having various configurations and locations of discharge openings or chutes somewhat different from the one shown and described herein. Also, it will be understood that prior art rotary mowers commonly draw air in only from underneath the deck or housing It but the vented mower disclosed herein permits the air to come from both underneath and above, and this produces an efficient grass blade agitating action and results in an improved smoother and more even cut and in highly compact bagging action when the cut grass is blown into a collector bag. Still further, the air vents described herein help prevent clogging or packing of grass underneath the mower housing and all of the incoming flow of air is not upwardly underneath the mower housing surface 37 but is also coming through the vents and downwardly into the annulus 16 and radially outwardly into the annulus l6.

Further, the drawings show that the vents 27 are located diametrically opposite the outlet opening 18 and extend around to a location adjacent the opening 18 and slightly therebeyond. The remainder of the housing 10 does not have the vents 27, so the housing strength is provided, and the maximum air flow is induced in the mower housing at a location immediately prior to the tangential discharge designated 20. Further, the total area of the vents 27 occupies a significant portion of the overall area of the housing 10, and, for example, the vents 27 are approximately one-fortieth of the area of the bottom of the housing or deck It as shown in these drawings. Also, the total area of the vents 27 is approximately one-fourth of the outlet area 18, as shown in these drawings.

The vents 27 are also disposed on the circular path coaxial with the cutter bar 12, but are arranged in size and spacing, and with the rings 32 and 33 and the webs 34 so that one cannot inadvertently insert a finger into I the path of the cutter ends 17 of the bar 12. The cutter ends 17 sweep a path substantially defining the aforementioned area of the bottom of the deck 10, and such area would be that seen or projected area of FIG. 2.

The rotary mower shown is of the self-propelled or powered propelled type wherein the wheels are driven for mobilizing the mower. Thus, the front two of the four wheels 11 are powered through the engine 23 and by means of a drive belt 38 extending around the hub 26 and two pulleys 39 and 41 and up to a pulley 42 at the front of the mower. A drive disc 43 is rotatablyconnected with the pulley 42 so that the two rotate together. A driven wheel 44 is on a shaft 46 which is rotatably supported on the front of the mower to be driven by the rotation of the wheel 44. In turn, and through any well-known or conventional arrangement, the front wheels 11 are rotatably driven in response to the rotation of the shaft 46. With this arrangement, operation of the engine 23 powers the belt 38 to rotate the disc 43 and drive the wheel 44 and in turn rotate the shaft 46 and drive the mower ground wheels 1 1. Of course the wheels 11 may be driven through the usual and well-known cammed gear which engages a ring gear in the wheels 11 for rotating the front wheels 11. Such arrangement of the drive gears for the wheels are conventional and need not be described herein.

FIGS. 1 and 3 show that the drive disc 43 is rotatably supported on an arm 47 which is pivotally mounted on the housing by means of a bolt or pin 48. Thus the arm 47 can pivot across the top of the mower housing 10 and thereby move the disc 43 to different locations relative to the upright plane of the driven wheel 44. It will then be understood that the speed of rotation of the wheel 44 will vary according to the position of the drive disc 43 in contact with the wheel 44.

The arm 47 has an upstanding pin 49 which engages a slot 51 in an arm 52 pivoted on the mower housing 10'by means of a screw 53. An operators control 54, which may be in the form of a Bowden wire, connects at its forward end to the pivot arm 52, and the rearend of the control 54 would extend back to the hand grip portion of the handle 22, in the usual and customary manner though the full extent of the control 54 is not would continue to rotate over the stalled wheel 44, and that would be undesirable in that a thumping would result when normal rotation resumed between the disc 43 and wheel 44.

Still further, it will be seen that the actual drive be tween the wheel 44 and the shaft 46 is through a set of gears 62 which are disposed in a pocket 63 formed right in the mower front portion 19. Thus the wheel 44 is normally and conventionally in rotational drive relation with a gear connected with the wheel 44, and, in turn, other gears in the gear cluster 62 are then rotated train shown. In this manner, a controlled speed reduction is achieved in the speed of rotation of the driving shown in these drawings. Thus the operator can manipulate the control 54 and thereby pivot the arm 52 which in turn moves the pin 49 and thus pivots the arm 47 so that the disc-43 would engage the wheel 44 at different points of radial contact on the disc 43. Thereby, the drive speed between the disc 43 and the wheel 44 can be varied. Also, a tension spring 56 connects to the arm 47 and extends down to be anchored on the forward deck 19 of the mower housing, and thus the spring 56 holds the arm 47 and the disc 43 downwardly for drive engagement with the wheel 44. A second control extends back to the handle 22 and includes another Bowden wire 57 which connects to a cam 58 pivoted on the side of the arm 47 by means of the pin 59. Thus rotation of the cam 58 by manipulation of the control 57 will cause the cam 58 to bear downwardly on the mower top surface and thus lift the arm 47 so that the disc 43 is clear of the wheel 44 and thereby the drive to the front wheels is disconnected. As such, the cam 58 and its arrangement with the arm 47 serves as a clutch.

The disc 43 has a rubber face 61 which engages the wheel 44 which is preferably of a hard material, such as a metal. Then, if the wheels 1 1 were held against rotation, such as by a stalling of the propelling of the mower, then the only thing that would occur would be the slight wearing of the rubber face 61 over the stationary wheel 44. Conversely, if the wheel 44 were rubber faced and stalling occurred, then the wheel 44 would have a flat spot worn onto it when the disc 43 disc 43, and also the mower portion 19 itself presents the gear box 64 which defines the gear cavity 63. The. box 64 is cast into and as a part of the mower housing, and FIG..4 shows the arrangement across the front of the mower, including the openings 66 which receive the bearings for supporting the shaft 46. Therefore, no separate and appended gear box need be provided, and the entire mower is arranged with the integral gear box and therefore a compact, lightweight, and sturdy mower housing is provided.

That is, while the propelling drive goes through the disc 43 and wheel 44 and to the shaft 46, it is transmit ted through the gear cluster 62, as described and shown. Also, the driving member is the disc 43 with the rubber face, rather than having the rubber face on the driven wheel 44, for the purpose mentioned. A belt tightener is provided in the form of a pivotal arm 67 which swings the belt pulley 39, and the arm 67 is under the influence of a tension spring 68, as seen in FIG. 1. Further, the belt 38 can be removed from the mower without removing the engine 23, simply by disconnecting the hub 26 from the engine shaft 24 and then sliding the belt 38 across the top of the mower housing 10 and toward the pulleys 39 and 41.

As previously mentioned, the mower handle 22 is only fragmentarily shown, but it would be understood that it is U-shaped and extends rearwardly to the usual hand grip portion where the operator can control the movement of the mower. The forward ends 69'of the legs of the handle 22 are pivotally connected to the mower by means of pins or bolts 71 supported on upstanding mower housing projections 72. In order to es tablish the desired angle or elevation for the handle 22, a standard 73 is pivotally supported on the mower projection 72 by means ofa bolt or pin 74. The upper end of the standard or support 73 carries a pin 76 which extends into one of three openings 77 on the mower handle end 69. Thus the upper end of the standard 73 and its pin 76 can be withdrawn from any one of the handle holes 77 and then re-inserted into another one of the holes 77 and thereby alter the angulation of the handle 22 relative to the mower housing 10. A compression coil spring 78 abuts the side of the standard 73 to yieldingly maintain the pin 76 in the selected one of the handle holes 77. It will also be seen that each of the legs of the handle 22 has a standard 73 with its attached pin 76, for the purpose just mentioned.

With this arrangement, the standard upper end 79 is extended above the handle end 69 and is therefore available for removing the pin 76 from one of the handle holes 77, without the requirement of any tools or any special skill or manipulation in re-positioning the pin 76. Also, it will be seen and understood that the handle 22 could be of the well-known folding type such as that shown in U. S. Pat. No. 2,727,753 where the handle folds downwardly to encircle the engine, and, in the present instance, there is nothing on the handle to interfere with the folding action, and the interengaging pin is on the standard 73, rather than having it on the handle. Further, the handle pin or bolt 71 is forward of the rear wheels 11, and thus any pushing by the operator on the handle 22 will be efficiently transmitted to the mower housing 10 at thepoint forward of the rear wheels 11, rather than having the pushing action force the rear wheels downwardly into the ground or even tip the rear end of the mower down. That is, the standards 73 serve to securely angulate the handles relative to the mower, and, at the same time, the handles can be readily released from the standard 73 for either repositioning the angulation or for folding the handle, and also the handle is disposed for maximum efficiency and the pushing action on the mower 10. Also, when the operator forces downwardly on the hand grip portion of the handle 22, then the standard 73 is simply placed under compression and is not weakened or damaged by such compressive force nor is it released from its support for the handle 22, which might be the occurrences if the pivot points between the handle. and the standard were reversed such that the standard would be placed in tension when the handle is pressed downwardly.

With regard to arm 47, it will be noted that its pivot mount-48 is halfway back on the housing 10 and this places it approximatelyv halfway between the front and rear wheels 1 1. It also places the mounting 48 adjacent the pulleys 39 and 41. Therefore, the arm 47 has a large pivot radius, and, upon swinging the arm 47 for changing the speeds of the mower, the belt 38 does not lose its tension since one extent of the belt 38 from the pulley 39 to the pulley 42 would either become more slack or have more tension, but, by virtueof the positioning of the pulleys 39 and 41, the belt 38 in its extent from the pulley 41 to the pulley 42 would accommodate the increased tension or slackness. Also, there is the belt tightener 68 effective on the tightener arm 67 for holding the belt 38 in tight condition.

The arm 52 has its slot 51 adjacent the pivot mounting 53 for the arm 52, and thus leverage is obtained in the actuation of the arm 52 and the consequent pivoting of the arm 47, so that the arm 47 can be easily moved when movement is desired. Further, the face 61 is of a resilient material, and it thus provides the necessary frictional contact with the circumference of the drive wheel 44, as mentioned. Further, the cam 58 is a clutch member which provides for disengagement of the drive disc 43 from the drive wheel 44. Also, the control 54 extends back to the hand grip portion of the handle 22, and it preferably has selectable .positions for setting the control 54, and thus setting the arm 52 and arm 47, in selected and fixed positions for holding the desired drive speed. U. S. Pat. No. 3,334,429 shows a type of disc and wheel drive, and it also shows controls extending from the drive and back to the operators handle, and these controls can be set in desired positio ns and retained therein, such as is commonly known in the lower portion of the depressed section 29 and thus are immediately adjacent the blade 12. Also, the vents 27 are then located in the forward portion of the mower housing 10, and the rearward portion is free of any vents, and such rearward portion extends for up to one-half the circular rear portion of the mower, as shown in FIG. 1. The vents 27 then extend from immediately adjacent the tangential chute 20 and the outlet 18 to the diametrically opposite side of the housing and underneath the speed control arm 47.

Also, the area of the vent openings 27 is such that the dimension of the vents along the line between each other is shown to be between one-half and one-third of the spacing or distance between every two openings 27, for ample air inlet opening and for adequate strength in the mower housing.

Further, the blade 12 has its ends 17 provided with the fanning portion or blade 81 which creates the air flow described. The fanning blades 81 draw the air into the cutting chamber 16, both from underneath the mower and through the openings 27, and the blades 81 also cause the air to move through the tangential outlet 20 and exhaust outlet 18. v

With regard to the driving disc 43, it is supported on a bearing 83 which is mounted on the arm 47', and the pulley 42 is also supported with the bearing 83. That is, the pulley 42 and the disc 43 are rotatably mounted on the arm 47 and they move with the swinging of the arm 47 about the pivot bolt 48. Also, the pivot bolt mounting 48 permits the up and down movement of the arm 47 under the influence of the cam 58 for engagement and disengagement of the-disc 43 relative to the driven wheel 44. Further, it will be understood that a protective stationary cover is commonly provided over the entire arm 47 and the pulleys 39 and 41, butsuch cover is not shown herein so that the moving parts can be more fully shown and described.

U. S. Pat. No. 3,462,924 also shows a U-shaped handle which is foldable over the mower engine, and it further shows a Bowden wire extending to a control at the handgrip end of the mower handle, and such arrangement could be used in this instance for controlling the clutch element described. Further, it will be seen that the pivot mountings for the handle 22 and the standard 73, namely the pins or bolts 71 and 74, and the point of intersection between the handle 22 and the standard 73, which is at the pin 76, form an equilateral triangle at least substantially so. With this arrangement the force on the handle is countered by compression in the standard 73, and the handle force is efficiently transmitted for either tipping the mower up off its propelling front wheels 11 or for pushing the mower in a forward direction. The standard 73 is yieldably urged to have its pin 76 enter one of the sockets or openings 77 by the urging of the compression spring 78.

What is claimed is:

l. A vented rotary lawn mower comprising a mower housing having a circular cutting chamber andan air outlet opening in air-flow communication with said chamber and having a top and a depending skirt extending downwardly from said top, ground wheels for movably supporting said housing with the lower edge of said skirt spaced slightly above the ground and for advancing said mower in a forward direction, a lawn cutter member rotatably supported in said housing and having grass cutters disposed in said chamber for cutting the grass and having an air-fanning portion for creating a flow of air in said chamber and out said outlet opening, said housing top having a plurality of air vent openings therein and disposed radially inwardly from said cutter member air-fanning portion and with said air vent openings being closely positioned adjacent each other across the forward portion of said housing from a location adjacent said outlet opening to a location diametrically opposite said outlet opening and along a curved line extending relative to the rotation of said cutter member, and a plurality of projections integral with and disposed on the underneath surface of said housing top and depending therefrom with one of said projections being disposed between every two of said air vent openings.

2. The vented rotary lawn mower as claimed in claim 1, wherein said projections are located adjacent said air vent openings on the upstream side thereof relative tothe direction of rotation of said cutter member and are located further away from said air vent openings at the downstream side thereof.

3. The vented rotary lawn mower as claimed in claim 1, including two radially spaced-apart rings integral with the underneath surface of saidhousing top and depending therefrom and being located on radially opposite sides of said curved line of air vent openings.

4. The vented rotary lawn mower as claimed in claim 3, including webs integral with said housing top and said rings and extending radially between said rings and intermediate every two of said air vent openings.

5. The vented rotary lawn mower as claimed in claim 4, wherein said websare located adjacent said air vent openings on the upstream side thereof relative to the direction of rotation of said cutter member and are located farther away from said air vent openings at the downstream side thereof.

6. The vented rotary lawn mower as claimed in claim 1, wherein the total area of said air vent openings is one-fourth the cross-sectional area of said air outlet opening.

7. The vented rotary lawn mower as claimed in claim 1, wherein said air vent openings are located radially inwardly relative to the location of said circular chamber, and said housing top has a depression therein extending along said curved line of said air vent openings, and said air vent openings are disposed along said de- 10 pression.

8. The vented rotary lawn mower as claimed in claim 1, wherein the remainder of said housing at the rear portion thereof is free of any of said air vent openings,

so that air enters said housing through said air vent openings only at said forward portion of said housing.

9. A vented rotary lawn mower comprising a mower housing having a circular cutting chamber and an air.

outlet opening in air-flow communication with said chamber and having a top and a depending skirt extending downwardly from said top, ground wheels for movably supporting said housing with the lower edge of said skirt spaced slightly above the ground and for advancing said mower in a forward direction, a lawn cutter member rotatably supported in said housing and having grass cutters disposed in said chamber for cutting the grass and having an air-fanning portion for creating a flow of air in said chamberand out said outlet opening, said housing top having a plurali'ty of air vent openings therein and disposed radially inwardly from said cutter member air-fanning portion and with said air vent openings being closely positioned adjacent each other across the forward portion of said housing from a location adjacentrsaid outlet opening to a location diametrically opposite said outlet opening and along a curved line extending relative to the rotation of said cutter member, two radially spacedapart rings integral with the underneath surface of said housing top and depending therefrom and being located on radially opposite sides of said curved line of air vent openings.

10. The vented rotary lawn mower as claimed in claim 9, including webs integral with said housing top and said rings and extending radially between said rings and intermediate every two of said air vent openings.

the downstream side thereof. 

1. A vented rotary lawn mower comprising a mower housing having a circular cutting chamber and an air outlet opening in air-flow communication with said chamber and having a top and a depending skirt extending downwardly from said top, ground wheels for movably supporting said housing with the lower edge of said skirt spaced slightly above the ground and for advancing said mower in a forward direction, a lawn cutter member rotatably supported in said housing and having grass cutters disposed in said chamber for cutting the grass and having an air-fanning portion for creating a flow of air in said chamber and out said outlet opening, said housing top having a plurality of air vent openings therein and disposed radially inwardly from said cutter member air-fanning portion and with said air vent openings being closely positioned adjacent each other across the forward portion of said housing from a location adjacent said outlet opening to a location diametrically opposite said outlet opening and along a curved line extending relative to the rotation of said cutter member, and a plurality of projections integral with and disposed on the underneath surface of said housing top and depending therefrom with one of said projections being disposed between every two of said air vent openings.
 2. The vented rotary lawn mower as claimed in claim 1, wherein said projections are located adjacent said air vent openings on the upstream side thereof relative to the direction of rotation of said cutter member and are located further away from said air vent openings at the downstream side thereof.
 3. The vented rotary lawn mower as claimed in claim 1, including two radially spaced-apart rings integral with the underneath surface of said housing top and depending therefrom and being located on radially opposite sides of said curved line of air vent openings.
 4. The vented rotary lawn mower as claimed in claim 3, including webs integral with said housing top and said rings and extending radially between said rings and intermediate every two of said air vent openings.
 5. The vented rotary lawn mower as claimed in claim 4, wherein said webs are located adjacent said air vent openings on the upstream side thereof relative to the direction of rotation of said cutter member and are located farther away from said air vent openings at the downstream side thereof.
 6. The vented rotary lawn mower as claimed in claim 1, wherein the total area of said air vent openings is one-fourth the cross-sectional area of said air outlet opening.
 7. The vented rotary lawn mower as claimed in claim 1, wherein said air vent openings are located radially inwardly relative to the location of said circular chamber, and said housing top has a depression therein extending along said curved line of said air vent openings, and said air vent openings are disposed along said depression.
 8. The vented rotary lawn mower as claimed in claim 1, wherein the remainder of said housing at the rear portion thereof is free of any of said air vent openings, so that air enters said housing through said air vent openings only at said forward portion of said housing.
 9. A vented rotary lawn mower comprising a mower housing having a circular cutting chamber and an air outlet opening in air-flow communication with said chamber and having a top and a depending skirt extending downwardly from said top, ground wheels for movably supporting said housing with the lower edge of said skirt spaced slightly above the ground and for advancing said mower in a forward direction, a lawn cutter member rotatably supporteD in said housing and having grass cutters disposed in said chamber for cutting the grass and having an air-fanning portion for creating a flow of air in said chamber and out said outlet opening, said housing top having a plurality of air vent openings therein and disposed radially inwardly from said cutter member air-fanning portion and with said air vent openings being closely positioned adjacent each other across the forward portion of said housing from a location adjacent said outlet opening to a location diametrically opposite said outlet opening and along a curved line extending relative to the rotation of said cutter member, two radially spaced apart rings integral with the underneath surface of said housing top and depending therefrom and being located on radially opposite sides of said curved line of air vent openings.
 10. The vented rotary lawn mower as claimed in claim 9, including webs integral with said housing top and said rings and extending radially between said rings and intermediate every two of said air vent openings.
 11. The vented rotary lawn mower as claimed in claim 10, wherein said webs are located adjacent said air vent openings on the upstream side thereof relative to the direction of rotation of said cutter member and are located farther away from said air vent openings at the downstream side thereof. 